1. Field of the Invention
The present invention relates to an automatic document feeder employed in copying machines, printers, facsimile machines, and the like that automatically transports original documents, and also relates to an image forming device comprising the same.
2. Background Information
Automatic document feeders employed in image forming devices such as copying machines, printers, and the like which automatically read image data and the like recorded on both sides of an original document are well known in the prior art.
This type of automatic document feeder is disclosed in Japanese Published Patent Applications H07-175279 and H09-106116. These devices are schematically illustrated in FIGS. 6 and 7.
The device shown in FIG. 6 is disposed along the path in which original documents D are transported (the path illustrated by the arrows a), and includes a loading tray 101, a pick-up roller 102, a paper supply roller 103, a pair of transport rollers 104, a transport drum 105, transport rollers 106, 107, and 108, a pair of discharge/reverse rollers 110, and a discharge tray 111. In addition, an original document reading position R is disposed between the transport rollers 107 and 108. Here, the upper surface of each original document D mounted in the loading tray 101 is the A side, and the lower surface thereof is the B side.
When only the A side of an original document D is to be read out, the original document D is supplied from the loading tray 101, the A side thereof is read, and is then discharged directly to the discharge tray 111 by the pair of discharge/reverse rollers 110. More specifically, a plurality of original documents D placed in the loading tray 101 are first supplied and transported one sheet at a time by the pick-up roller 102, the paper supply roller 103, and the pair of transport rollers 104. Next, while each original document D is transported by the transport drum 105 and the transport rollers 106, 107, and 108, the A side thereof is read at the original document reading position R. Then, after the A side of each original document D is read, they are transported in the direction illustrated by the arrow a by rotating the discharge/reverse rollers 110 in the directions shown, and are then discharged to the discharge tray 111 with the A side thereof facing downward.
In contrast, when both the A side and the B side of an original document D are to be read, after the A side thereof is read, the original document D is transported in the direction of the arrows a by rotating the discharge/reverse rollers 110 in the same direction as described above. However, when the trailing edge of the original document D reaches the discharge/reverse rollers 110, the discharge/reverse rollers 110 will reverse their rotations. Thus, each original document D is transported in the direction illustrated by the arrow b, transported to the original document reading position R by means of the transport drum 105 and the transport rollers 106, 107, and 108 such that the B side of each is facing away from the transport drum 105, and the B side of each is then read. After the B side of each original document D is read, each is transported around the transport drum 105, and is discharged to the discharge tray 111. More specifically, after the B side of the original document D is read, it is transported in the direction illustrated by the arrows a by rotating the discharge/reverse rollers 110 in the directions shown, and when the trailing edge of each reaches the discharge/reverse rollers 110, each is transported in the direction illustrated by the arrow b by reversing the rotation of the discharge/reverse rollers 110. Then, each original document D will transported by the transport drum 105 and the transport rollers 106, 107, and 108 and discharged to the discharge tray 111 without being read. When this occurs, each original document D will be discharged with the A side of each facing downward.
FIG. 7 will now be described.
The device shown in FIG. 7 eliminates the structure used to reverse the orientation of the A and B sides of an original document D. Because the device shown in FIG. 7 has the same basic structure as the automatic document feeder shown in FIG. 6, only the differences between it and the device of FIG. 6 will be described below.
This automatic document feeder is comprised of a drive roller 112, driven rollers 113, 114, a switching claw 115, a pair of reverse rollers 116, and an intermediate tray 117. Note that in this device, the drive roller 112 and the driven roller 113 below it form a pair of discharge rollers.
In this device, the switching claw 115 is placed in the position indicated by the dotted lines when only the A side of an original document D is to be read, and after the A side thereof is read, the original document D is discharged to the discharge tray 111 by rotating the drive roller 112 in the direction indicated by the arrow.
In contrast, when both the A side and the B side of an original document D are to be read, after the A side thereof is read, the switching claw 115 is placed in the position indicated by the solid lines, and the original document D is guided to the intermediate tray 117 by rotating the drive roller 112 and the pair of reverse rollers 116 in the directions indicated by the respective arrows.
When the trailing edge of the original document D reaches the reverse rollers 116, the reverse rollers 116 reverse rotation, transport the original document D in the direction illustrated by the arrow b, and the B side thereof is then read at the original document reading position R. After the B side of the original document D is read, the orientation of the A and B sides is reversed and the original document D is discharged to the discharge tray 111. More specifically, after the B side of an original document D is read, the switching claw 115 will be placed in the position indicated by the solid lines, and will be guided to the intermediate tray 117 by rotating the drive roller 112 and the reverse rollers 116 in the direction indicated by the respective arrows. Then, when the trailing edge of the original document D reaches the reverse rollers 116, the reverse rollers 116 will reverse rotation, and will then transport the original document D in the direction indicated by the arrow b. The original document D is not read at this point. The switching claw 115 is placed in the position shown by the dotted line, and by rotating the drive roller 112 in the direction indicated by the arrow, the original document D is discharged to the discharge tray 111 with the A side thereof facing upward.
As noted above, in an automatic document feeder that can automatically read both sides (the A side and B side) of an original document D, it is preferable that the pair of reverse rollers be disposed a relatively short distance away from the original document reading position R, and that the pair of discharge rollers be disposed a relatively long distance way from the original document reading position R.
The reason for the former is that when the pair of reverse rollers is relatively far away from the original document reading position R, the pair of reverse rollers will also be relatively far away from the adjacent transport members (the transport rollers 106 or 108 in the example of FIG. 6), and thus an original document that is not large enough to extend between the pair of reverse rollers and an adjacent transport member cannot be transported thereby. In addition, in this situation, the original document transport path will be long, and thus the time needed to read the original document (especially the time needed to read the B side and then switch the orientation of the A and B sides) will increase. Note that in situations in which the distance between the reverse rollers and the adjacent transport members is relatively long, a small original document (one whose length in the transport direction is short) can be handled if a separate transport member is added in between the reverse rollers and the adjacent transport members. However, this will complicate the automatic document feeder.
The reason for the latter is that when the pair of reverse rollers is relatively close to the original document reading position R, an original document D is discharged to a position further inside the device (the left side in FIGS. 6 and 7), and thus an original document D discharged to the discharge tray 111 cannot be easily seen due to the presence of the loading tray 101 or the intermediate tray 117. Note that, in general, a person using the device can confirm that an original document D has been discharged to the discharge tray 111 by looking diagonally into the space between the loading tray 101 and the discharge tray 111.
Thus, regardless of whether it is preferable to have the reverse rollers relatively close to the original document reading position R, or whether it is preferable to have the discharge rollers relatively far away from the original document reading position R, neither of these structures can be achieved with the device shown in FIG. 6 because the device shown therein includes discharge/reverse rollers 110 which function as both reverse rollers and discharge rollers. More specifically, when the discharge/reverse rollers 110 are positioned relatively close to the original document reading position R, the original document discharge position will shift further toward the interior of the device than the loading tray 101 (the left side in FIG. 6), and an original document D that has been discharged to the discharge tray 111 will be less visible to a person operating the device. On the other hand, when the discharge/reverse rollers 110 are positioned relatively far away from the original document reading position R, an original document D discharged to the discharge tray 111 is easier to see, but the original document reading position R will be relatively far away from the discharge/reverse rollers 110, and thus the time needed to read an original document will increase.
In the automatic document feeder shown in FIG. 7, the reverse rollers 116 are disposed relatively far away from the original document reading position R, and the discharge rollers (the drive roller 112 and the driven roller 113) are disposed relatively close to the original document reading position R. Thus, when both sides of an original document D are to be read, the time needed to read them will be longer, and it will be difficult to confirm that the original document D has been discharged to the discharge tray 111.
It is therefore an object of the present invention to separate the reverse rollers from the discharge rollers, and by optimally setting the positional relationship between the reverse rollers and the discharge rollers, make it possible to read original documents whose length in the transport direction is short, reduce the time needed to read both sides of an original document, and increase the visibility of original documents when they are discharged.
An automatic document feeder according to one aspect of the present invention is comprised of a loading unit, a supply device, a discharge device, a discharge unit, and a reversing device. Original documents are laded into the loading unit. The supply device supplies the original documents loaded in the loading unit to an original document reading position. The discharge device discharges the original documents which were read at the original document reading position. The discharge unit supports the original documents discharged by the discharge device. The reversing device is disposed below the loading unit and above the discharge device, and reverses the orientation each original document with respect to the original document reading position and then re-supplies them to the original document reading position. The reversing device and the discharge device are disposed such that the distance in the horizontal direction from the original document reading position to the discharge device is longer than the distance in the horizontal direction from the original document reading position to the reversing device.
According to another aspect of the present invention, the reversing device has an upper reverse roller and a lower reverse roller that form a reverse nip that grasps and transports an original document by mutually contacting the original document in a substantially vertical direction.
According to another aspect of the present invention, the discharge device has an upper discharge roller and a lower discharge roller that forms a discharge nip that grasps and transports an original document by mutually contacting the original document in a substantially vertical direction.
According to another aspect of the present invention, the reverse nip is disposed above the discharge nip.
According to another aspect of the present invention, the automatic document feeder further comprises a switching member. The switching member can be selectively placed in either the reverse position in order to guide an original document read at the original document reading position to the reverse nip unit, or the discharge position in order to guide an original document read at the original document reading position to the discharge nip.
According to another aspect of the present invention, an automatic document feeder further comprises an intermediate support member that supports a first end of an original document while a second end of the original document is in the grasp of the reverse nip.
In another aspect of the present invention, an image forming device comprises an original document reading device, an automatic document feeder, an image forming unit, and a recording media transport device. The original document reading device reads an original document in an original document reading position. The automatic document feeder is the device disclosed above that supplies the original document to the original document reading position, and transports the original document read at the original document reading position away therefrom. The image forming unit forms an image on the recording media based upon image data read by the original document reading device. The recording media transport device supplies recording media to the image forming unit, and transports the recording media on which an image has been formed away therefrom.
These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.